2016 Ford F150 5.0
I noticed this noise with the hood up. I never heard it before when driving (not sure if you can hear it while driving) but i have only owned the truck for 2 days.Its sorta thumping at random intervals. This was a cold engine and i ran it until it came up to temp. What started my investigation was i noticed my coolant was low. I grabbed a funnel and poured in some coolant. After that i noticed i had coolant on the hoses dripping down to the cross member and onto the road. Since i was careful and used a funnel i don't think it was me, but its possible. While cleaning up i noticed coolant on the pulleys and on the electric fans. I know i didn't do that, so i thought maybe something was leaking while driving and it caused it to go into the fans. So while i was letting it warm up to see if anything leaked is when i noticed the noise. The temp gauge went to the middle and heater was hot. The electric fans never kicked on though.
Anyway, that odd noise worries me, is it fuel? a relay or solenoid? I can't seem to attach the video but here it is in dropbox weird engine noise

 

I want to add that the truck drives fine. No stuttering, no loss of power.

 

I went out there this morning. The random hollow thumping noise does not appear on cold start. Once engine warms up and the revs change, then the noise starts. Its loud enough to hear with the hood down, but you can't hear it or feel it in the cab. I can't seem to get it hot enough for the fans to kick on, unless this noise is from trying to start the fans.

 

Sounds like the thumping sound I've had with my old 2013 f150 and niw my current 2019 f150 along with about a dozen f150 rentals I've had while on vacation or for work.

Next drive after it comes up to temp see if you can reproduce it my putting truck in gear with foot on the brake a hold RPMs right around 900-1,100 and listen for it

 

I've been told its the throttle body. I wouldn't be able to hear it in the cab, i've been driving it around just fine and i can't hear it unless i pop the hood.

 

You're not addressing the coolant leak? it'll be one of the quick connect fittings under the expansion tank most likely.

 

I cleaned up the leaked coolant. It was on my fans, the crank, top of the motor. It looked like a giant leak and the fans spread it around while i was driving. After i filled the expansion tank and cleaned it all up, i drove about 150 miles and checked again. No leak, the fluid level is exactly where i left off. I don't know what happened. Maybe the expansion tank lid wasn't tight to begin with?
When i did clean up the link, it looked like it was leaking at the quick connect fittings, but no there is no leak anywhere. Going to keep my eye on it.

 

Does this sound you are referring to sound similar to this by chance? you can hear it pretty good starting at about the 17 second point in the video